*
* $Id$
*
* $Log: caspip.F,v $
* Revision 1.2  2002/07/10 09:45:00  morsch
* Gheisha corrections suggested by Gary Bower (FNAL).
*
* Revision 1.1.1.1  1995/10/24 10:21:00  cernlib
* Geant
*
*
#include "geant321/pilot.h"
*CMZ :  3.21/02 29/03/94  15.41.38  by  S.Giani
*-- Author :
      SUBROUTINE CASPIP(K,INT,NFL)
C
C *** CASCADE OF PI+ ***
C *** NVE 04-MAY-1988 CERN GENEVA ***
C
C ORIGIN : H.FESEFELDT (18-SEP-1987)
C
C PI+  UNDERGOES INTERACTION WITH NUCLEON WITHIN NUCLEUS.
C CHECK IF ENERGETICALLY POSSIBLE TO PRODUCE PIONS/KAONS.
C IF NOT ASSUME NUCLEAR EXCITATION OCCURS AND INPUT PARTICLE
C IS DEGRADED IN ENERGY.    NO OTHER PARTICLES PRODUCED.
C IF REACTION IS POSSIBLE FIND CORRECT NUMBER OF PIONS/PROTONS/
C NEUTRONS PRODUCED USING AN INTERPOLATION TO MULTIPLICITY DATA.
C REPLACE SOME PIONS OR PROTONS/NEUTRONS BY KAONS OR STRANGE BARYONS
C ACCORDING TO AVERAGE MULTIPLICITY PER INELASTIC REACTIONS.
C
#include "geant321/mxgkgh.inc"
#include "geant321/s_consts.inc"
#include "geant321/s_curpar.inc"
#include "geant321/s_result.inc"
#include "geant321/s_prntfl.inc"
#include "geant321/limits.inc"
#include "geant321/s_kginit.inc"
C
      REAL N
      DIMENSION PMUL(2,1200),ANORM(2,60),SUPP(10),CECH(10),B(2)
      DIMENSION RNDM(1)
      SAVE PMUL,ANORM
      DATA SUPP/0.,0.4,0.55,0.65,0.75,0.82,0.86,0.90,0.94,0.98/
      DATA CECH/1.0,0.95,0.79,0.32,0.19,0.16,0.14,0.12,0.1,0.08/
      DATA B/0.7,0.7/,C/1.25/
C
C --- INITIALIZATION INDICATED BY KGINIT(18) ---
      IF (KGINIT(18) .NE. 0) GO TO 10
      KGINIT(18)=1
C
C --- INITIALIZE PMUL AND ANORM ARRAYS ---
      DO 9000 J=1,1200
      DO 9001 I=1,2
      PMUL(I,J)=0.0
      IF (J .LE. 60) ANORM(I,J)=0.0
 9001 CONTINUE
 9000 CONTINUE
C
C** COMPUTE NORMALIZATION CONSTANTS
C** FOR P AS TARGET
C
      L=0
      DO 1 NP1=1,20
      NP=NP1-1
      NMM1=NP1-2
      IF(NMM1.LE.1) NMM1=1
      DO 1 NM1=NMM1,NP1
      NM=NM1-1
      DO 1 NZ1=1,20
      NZ=NZ1-1
      L=L+1
      IF(L.GT.1200) GOTO 1
      NT=NP+NM+NZ
      IF(NT.LE.0.OR.NT.GT.60) GOTO 1
      PMUL(1,L)=PMLTPC(NP,NM,NZ,NT,B(1),C)
      ANORM(1,NT)=ANORM(1,NT)+PMUL(1,L)
    1 CONTINUE
C** FOR N AS TARGET
      L=0
      DO 2 NP1=1,20
      NP=NP1-1
      NMM1=NP1-1
      IF(NMM1.LE.1) NMM1=1
      NPP1=NP1+1
      DO 2 NM1=NMM1,NPP1
      NM=NM1-1
      DO 2 NZ1=1,20
      NZ=NZ1-1
      L=L+1
      IF(L.GT.1200) GOTO 2
      NT=NP+NM+NZ
      IF(NT.LE.0.OR.NT.GT.60) GOTO 2
      PMUL(2,L)=PMLTPC(NP,NM,NZ,NT,B(2),C)
      ANORM(2,NT)=ANORM(2,NT)+PMUL(2,L)
    2 CONTINUE
      DO 3 I=1,60
      IF(ANORM(1,I).GT.0.) ANORM(1,I)=1./ANORM(1,I)
      IF(ANORM(2,I).GT.0.) ANORM(2,I)=1./ANORM(2,I)
    3 CONTINUE
      IF(.NOT.NPRT(10)) GOTO 10
      WRITE(NEWBCD,2001)
      DO 4 NFL=1,2
      WRITE(NEWBCD,2002) NFL
      WRITE(NEWBCD,2003) (ANORM(NFL,I),I=1,60)
      WRITE(NEWBCD,2003) (PMUL(NFL,I),I=1,1200)
    4 CONTINUE
C**  CHOOSE PROTON OR NEUTRON AS TARGET
   10 NFL=2
      CALL GRNDM(RNDM,1)
      IF(RNDM(1).LT.ZNO2/ATNO2) NFL=1
      TARMAS=RMASS(14)
      IF (NFL .EQ. 2) TARMAS=RMASS(16)
      S=AMASQ+TARMAS**2+2.0*TARMAS*EN
      RS=SQRT(S)
      ENP(8)=AMASQ+TARMAS**2+2.0*TARMAS*ENP(6)
      ENP(9)=SQRT(ENP(8))
      EAB=RS-TARMAS-RMASS(7)
C
C**  ELASTIC SCATTERING
      NP=0
      NM=0
      NZ=0
      N=0.
      IPA(1)=7
      IPA(2)=14
      IF(NFL.EQ.2) IPA(2)=16
      IF(INT.EQ.2) GOTO 20
      GOTO 100
  20  CONTINUE
C**  SUPPRESSION OF HIGH MULTIPLICITY EVENTS AT LOW MOMENTUM
      IEAB=IFIX(EAB*5.)+1
      IF(IEAB.GT.10) GOTO 22
      CALL GRNDM(RNDM,1)
      IF(RNDM(1).LT.SUPP(IEAB)) GOTO 22
C**  CHARGE EXCHANGE REACTION
      IPLAB=IFIX(P   *5.)+1
      IF(IPLAB.GT.10) IPLAB=10
      CALL GRNDM(RNDM,1)
      IF(RNDM(1).GT.CECH(IPLAB)) GOTO 23
      IF(NFL .EQ. 2)GOTO 24
      INT = 1
      IPA(1) = 7
      IPA(2) = 14
      GOTO 100
  24  CONTINUE
      IPA(1)=8
      IPA(2)=14
      GOTO 100
 23   CONTINUE
C**  CHECK IF ENERGETICALLY POSSIBLE TO PRODUCE ONE EXTRA PION IN REACT.
      IF(EAB .LE. RMASS(7))GOTO 55
      N = 1.
      IF(NFL .EQ. 2)GOTO 26
      TEST=-(1+B(1))**2/(2.0*C**2)
      IF (TEST .LE. EXPXL) TEST=EXPXL
      IF (TEST .GE. EXPXU) TEST=EXPXU
      W0=EXP(TEST)
      WP=EXP(TEST)
      CALL GRNDM(RNDM,1)
      RAN=RNDM(1)
      NP=0
      NM=0
      NZ=1
      IF(RAN.LT.W0/(W0+WP)) GOTO 50
      NP=1
      NM=0
      NZ=0
      GOTO 50
 26   CONTINUE
      TEST=-(1+B(2))**2/(2.0*C**2)
      IF (TEST .LE. EXPXL) TEST=EXPXL
      IF (TEST .GE. EXPXU) TEST=EXPXU
      W0=EXP(TEST)
      WP=EXP(TEST)
      TEST=-(B(2)-1)**2/(2.0*C**2)
      IF (TEST .LE. EXPXL) TEST=EXPXL
      IF (TEST .GE. EXPXU) TEST=EXPXU
      WM=EXP(TEST)
      WT=W0+WP+WM
      WP=W0+WP
      CALL GRNDM(RNDM,1)
      RAN=RNDM(1)
      NP=0
      NM=0
      NZ=1
      IF(RAN.LT.W0/WT) GOTO 50
      NP=1
      NM=0
      NZ=0
      IF(RAN.LT.WP/WT)GOTO 50
      NP=0
      NM=1
      NZ=0
      GOTO 50
C
   22 ALEAB=LOG(EAB)
C** NO. OF TOTAL PARTICLES VS SQRT(S)-2*MP
      N=3.62567+0.665843*ALEAB+0.336514*ALEAB*ALEAB
     * +0.117712*ALEAB*ALEAB*ALEAB+0.0136912*ALEAB*ALEAB*ALEAB*ALEAB
      N=N-2.
C** NORMALIZATION CONSTANT FOR  KNO-DISTRIBUTION
      ANPN=0.
      DO 21 NT=1,60
      TEST=-(PI/4.0)*(NT/N)**2
      IF (TEST .LE. EXPXL) TEST=EXPXL
      IF (TEST .GE. EXPXU) TEST=EXPXU
      DUM1=PI*NT/(2.0*N*N)
      DUM2=ABS(DUM1)
      DUM3=EXP(TEST)
      ADDNVE=0.0
      IF (DUM2 .GE. 1.0) ADDNVE=DUM1*DUM3
      IF ((DUM2 .LT. 1.0) .AND. (DUM3 .GE. 1.0E-10)) ADDNVE=DUM1*DUM3
      ANPN=ANPN+ADDNVE
   21 CONTINUE
      ANPN=1./ANPN
C** P OR N AS TARGET
      CALL GRNDM(RNDM,1)
      RAN=RNDM(1)
      EXCS=0.
      GOTO (30,40),NFL
C** FOR P AS TARGET
   30 L=0
      DO 31 NP1=1,20
      NP=NP1-1
      NMM1=NP1-2
      IF(NMM1.LE.1) NMM1=1
      DO 31 NM1=NMM1,NP1
      NM=NM1-1
      DO 31 NZ1=1,20
      NZ=NZ1-1
      L=L+1
      IF(L.GT.1200) GOTO 31
      NT=NP+NM+NZ
      IF(NT.LE.0.OR.NT.GT.60) GOTO 31
      TEST=-(PI/4.0)*(NT/N)**2
      IF (TEST .LE. EXPXL) TEST=EXPXL
      IF (TEST .GE. EXPXU) TEST=EXPXU
      DUM1=ANPN*PI*NT*PMUL(1,L)*ANORM(1,NT)/(2.0*N*N)
      DUM2=ABS(DUM1)
      DUM3=EXP(TEST)
      ADDNVE=0.0
      IF (DUM2 .GE. 1.0) ADDNVE=DUM1*DUM3
      IF ((DUM2 .LT. 1.0) .AND. (DUM3 .GE. 1.0E-10)) ADDNVE=DUM1*DUM3
      EXCS=EXCS+ADDNVE
      IF(RAN.LT.EXCS) GOTO 50
   31 CONTINUE
      GOTO 80
C** FOR N AS TARGET
   40 L=0
      DO 41 NP1=1,20
      NP=NP1-1
      NMM1=NP1-1
      IF(NMM1.LE.1) NMM1=1
      NPP1=NP1+1
      DO 41 NM1=NMM1,NPP1
      NM=NM1-1
      DO 41 NZ1=1,20
      NZ=NZ1-1
      L=L+1
      IF(L.GT.1200) GOTO 41
      NT=NP+NM+NZ
      IF(NT.LE.0.OR.NT.GT.60) GOTO 41
      TEST=-(PI/4.0)*(NT/N)**2
      IF (TEST .LE. EXPXL) TEST=EXPXL
      IF (TEST .GE. EXPXU) TEST=EXPXU
      DUM1=ANPN*PI*NT*PMUL(2,L)*ANORM(2,NT)/(2.0*N*N)
      DUM2=ABS(DUM1)
      DUM3=EXP(TEST)
      ADDNVE=0.0
      IF (DUM2 .GE. 1.0) ADDNVE=DUM1*DUM3
      IF ((DUM2 .LT. 1.0) .AND. (DUM3 .GT. 1.0E-10)) ADDNVE=DUM1*DUM3
      EXCS=EXCS+ADDNVE
      IF(RAN.LT.EXCS) GOTO 50
   41 CONTINUE
      GOTO 80
   50 GOTO (60,65),NFL
   60 IF(NP.EQ.1+NM) GOTO 61
      IF(NP.EQ.2+NM) GOTO 63
      IPA(1)=7
      IPA(2)=14
      GOTO 100
   61 CALL GRNDM(RNDM,1)
      IF(RNDM(1).LT.0.5) GOTO 62
      IPA(1)=7
      IPA(2)=16
      GOTO 100
   62 IPA(1)=8
      IPA(2)=14
      GOTO 100
   63 IPA(1)=8
      IPA(2)=16
      GOTO 100
   65 IF(NP.EQ.NM) GOTO 66
      IF(NP.EQ.1+NM) GOTO 68
      IPA(1)=7
      IPA(2)=14
      GOTO 100
   66 CALL GRNDM(RNDM,1)
      IF(RNDM(1).LT.0.25) GOTO 67
      IPA(1)=7
      IPA(2)=16
      GOTO 100
   67 IPA(1)=8
      IPA(2)=14
      GOTO 100
   68 IPA(1)=8
      IPA(2)=16
      GOTO 100
   70 IF(NPRT(4))
     *WRITE(NEWBCD,1003) EAB,N,NFL,NP,NM,NZ
      CALL STPAIR
      IF(INT.EQ.1) CALL TWOB(7,NFL,N)
      IF(INT.EQ.2) CALL GENXPT(7,NFL,N)
      GO TO 9999
   55 IF(NPRT(4))
     *WRITE(NEWBCD,1001)
      GOTO 53
C** EXCLUSIVE REACTION NOT FOUND
   80 IF(NPRT(4))
     *WRITE(NEWBCD,1004) RS,N
   53 INT=1
      NP=0
      NM=0
      NZ=0
      N=0.
      IPA(1)=7
      IPA(2)=14
      IF(NFL.EQ.2) IPA(2)=16
  100 DO 101 I=3,60
  101 IPA(I)=0
      IF(INT.LE.0) GOTO 131
  120 NT=2
      IF(NP.EQ.0) GOTO 122
      DO 121 I=1,NP
      NT=NT+1
  121 IPA(NT)=7
  122 IF(NM.EQ.0) GOTO 124
      DO 123 I=1,NM
      NT=NT+1
  123 IPA(NT)=9
  124 IF(NZ.EQ.0) GOTO 130
      DO 125 I=1,NZ
      NT=NT+1
  125 IPA(NT)=8
  130 IF(NPRT(4))
     *WRITE(NEWBCD,2004) NT,(IPA(I),I=1,20)
      IF(IPA(1).EQ.7) NP=NP+1
      IF(IPA(1).EQ.8) NZ=NZ+1
      IF(IPA(1).EQ.9) NM=NM+1
      GOTO 70
  131 IF(NPRT(4))
     *WRITE(NEWBCD,2005)
C
1001  FORMAT('0*CASPIP* CASCADE ENERGETICALLY NOT POSSIBLE',
     $ ' CONTINUE WITH QUASI-ELASTIC SCATTERING')
1003  FORMAT(' *CASPIP* PION+ -INDUCED CASCADE,',
     $ ' AVAIL. ENERGY',2X,F8.4,
     $ 2X,'<NTOT>',2X,F8.4,2X,'FROM',4(2X,I3),2X,'PARTICLES')
1004  FORMAT(' *CASPIP* PION+ -INDUCED CASCADE,',
     $ ' EXCLUSIVE REACTION NOT FOUND',
     $ ' TRY ELASTIC SCATTERING  AVAIL. ENERGY',2X,F8.4,2X,
     $ '<NTOT>',2X,F8.4)
2001  FORMAT('0*CASPIP* TABLES FOR MULT. DATA PION+  INDUCED REACTION',
     $ ' FOR DEFINITION OF NUMBERS SEE FORTRAN CODING')
2002  FORMAT(' *CASPIP* TARGET PARTICLE FLAG',2X,I5)
2003  FORMAT(1H ,10E12.4)
2004  FORMAT(' *CASPIP* ',I3,2X,'PARTICLES , MASS INDEX ARRAY',2X,20I4)
2005  FORMAT(' *CASPIP* NO PARTICLES PRODUCED')
C
 9999 CONTINUE
      END
